What is skill and how is it acquired?
There are two rooms in my house that have recently been repainted, one by a professional decorator, the other by me. The decorator was skilled at his job. I was not. By what marks might one detect the difference? Well, the end product certainly tells something. If you look closely at the walls that I painted you will find unevenness of texture; too much paint here, barely enough to cover there. You will find faint vertical streaks where the paint has run, and you will find small overshoots and undershoots at the edges. The walls painted by the professional are even in texture, and the edges are beautifully straight.